Russia remains ready to act as a mediator in the conflict between Israel and Iran, and Moscow's previous proposal to store Iranian uranium in Russia remains on the table, the Kremlin said on Monday.

Tehran says it has the right to peaceful nuclear power, but its swiftly-advancing uranium enrichment programme has raised fears in the wider West and across the Gulf that it wants to develop a nuclear weapon.

Before Israel launched strikes on the Islamic Republic, Russia said last week that it stood ready to remove highly enriched uranium from Iran and convert it into civilian reactor fuel as a potential way to calm the crisis.

"This proposal remains on the table, it remains relevant. But, of course, with the outbreak of hostilities, the situation has become seriously complicated," Kremlin spokesman Dmitry Peskov said.

U.S. President Donald Trump expressed optimism on Sunday that peace would come soon and cited the possibility that Russian President Vladimir Putin could help.

Russia, Peskov said, remained ready to mediate if needed, but he noted the root causes of the conflict needed to be addressed and eliminated - and that the military strikes were escalating the entire crisis to beyond serious levels.

"Russia remains ready to do everything necessary to eliminate the root causes of this crisis," Peskov said. "But the situation is escalating more than seriously, and, of course, this is not affecting the situation for the better."

Asked about Israeli Prime Minister Benjamin Netanyahu's remarks to Fox News on Sunday that regime change in Iran could be a result of Israel's military attacks, Peskov said that the Kremlin had seen the remarks.

"You know that we condemn those actions that have led to such a dangerous escalation of tension in the region," Peskov said. "And secondly, we also note a significant consolidation of society in Iran against the background of the bombing that is currently being carried out by the Israeli side."